Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.
Supernova Explosion. When the dragon dies, its body forcibly explodes in a burst of extreme radiance. Each creature within 30 feet of it is blinded for 1 minute and must make a DC 23 Constitution saving throw. On a failed save, a creature suffers one level of fatigue, takes (6d6) fire damage and (6d6) radiant damage, and is pushed 30 feet away from the dragon and knocked prone. On a successful save, the creature takes half as much damage but suffers no other effects. A blinded creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. The explosion leaves behind a blazing hot star ruby known as an adult solar heart.
Undying Light. The dragon perpetually sheds bright light in a 45-foot radius and dim light for an additional 45 feet. This light is sunlight. Also the dragon heals 20 hit points at the start of it's turn as long as it isn't in an area of magic darkness or takes necrotic damage since it's last turn.
Gleaming Brilliance (1/Day). When the dragon is first bloodied, it immediately recharges its breath weapon, if it’s not already available. After doing so, the dragon’s golden scales melt, coating its body in a layer of plasma. A creature that touches the dragon or hits it with a melee attack for the first time on a turn takes (3d6) fire damage.
Multiattack. The dragon can use its Solar Flare. It then makes three attacks: one with its Bite, Molten Spit or Tail and two with its Claws.
Bite. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: (2d10 + 7) piercing damage plus (1d6) fire and (1d6) radiant damage.
Claw. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: (2d6 + 7) slashing damage.
Tail. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: (2d8 + 7) bludgeoning damage.
Molten Spit. The dragon targets one creature within 60 feet, forcing it to make a DC 23 Dexterity saving throw. The creature takes (4d10) fire damage on a failure or half on a success. Liquid gold pools in a 5-foot-square occupied by the creature and remains hot for 1 minute. A creature that ends its turn in the gold or enters it for the first time on a turn takes (3d10) fire damage. At the beginning of the dragons next turn when it rolls for it's breath attack recharge, if this attack was used last turn the dice to recharge is instead a 4-6.
Solar Flare. The dragon emits a wave of overwhelmingly brilliant light. Each creature within 60 feet of it must succeed on a DC 23 Constitution saving throw or be blinded until the end of the turn. In addition, roll a d6. On a 6, the dragon can immediately use its Plasma Breath, regardless of whether it is charged or not; if it does so, it can’t make attacks for the rest of the turn.
Plasma Breath (Recharge 5–6). The dragon exhales a corona of solar energy in a 90-foot cone. Each creature in that area must make a DC 23 Constitution saving throw, taking 24 (7d6) fire damage and 24 (7d6) radiant damage on a failed save, or half as much damage on a successful one. Whether the saving throw is successful or not, a target can’t take reactions until the end of the dragon’s next turn.
Roar. Each creature of the dragon’s choice within 120 feet that can hear it makes a DC 19 Wisdom saving throw. On a failure, it is frightened for 1 minute. A creature repeats the saving throw at the end of its turns, ending the effect on itself on a success. When it succeeds on a saving throw or the effect ends for it, it is immune to Roar for 24 hours
The dragon can take 4 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The dragon regains spent legendary actions at the start of its turn.
Move. The dragon moves up to half its speed this movement does not provoke oppertuantity attacks.
Tail Attack. The dragon makes a tail attack.
Gravity Well (Costs 2 Actions). The dragon intensifies the gravitational pull around itself, concentrating it into a crushing force. Each creature of the dragon’s choice within 40 feet of it must make a DC 23 Strength saving throw. On a failed save, a creature takes 11 (2d10) force damage and is pulled up to 20 feet toward the dragon. On a successful save, the creature takes half as much damage and isn’t pulled.
Fiery Reprisal (Costs 2 Actions). The dragon uses Molten Spit against the last creature to deal damage to it.
Action Recovery (Costs 3 Actions). The dragon can spend 3 Legendary Actions to remove 1 of the following conditions from itself: Charmed, Confused, Numbed, Paralyzed, Rattled, Stunned.
Bloodied Legendary Actions
Elite Recovery (Replaces Action Recovery). The dragon ends one negative effect currently affecting it. It can do so as long as it has at least 1 hit point, even while unconscious or incapacitated.
Mortal Terror (Gaze). A creature within 120 feet makes a saving throw against Roar, even if it has already successfully saved within the past 24 hours.
Lair and Lair Actions
On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one ofthe following effects:
Debilitating waves of cosmic energy radiate from a point the dragon can see within 120 feet of it. Each creature within 30 feet of that point must succeed on a DC 15 Constitution saving throw or become poisoned for 1 minute and suffer one level of Fatigue or Strife. A creature can repeat the saving throw at the end of each of its turns, ending the poisoned condition and any levels of Fatigue/Strife caused by this effect on a success.
Beams of radiance shower the area near the dragon. Up to 3 creatures of the dragon’s choice within 120 feet of it must make a DC 15 Dexterity saving throw. On a failed save, a target takes (4d6) radiant damage and then begins to emit bright light in a 5-foot radius and dim light for an additional 5 feet until initiative count 20 on the next round. While this light persists, the creature can’t benefit from being invisible, and whenever it takes radiant damage, it takes an extra (2d6)radiant damage.
The force of gravity intensifies in the dragon’s vicinity. Each creature of the dragon’s choice within 60 feet of it must succeed on a DC 15 Strength saving throw or fall prone and become restrained for 1 minute or until the dragon uses another lair action or dies. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.